Abstract
A series of cathodic polarization experiments for DH36 steel has been performed with seawater flow in a range of flow velocities: 0.20, 0.40, 0.60, 0.80, 1.00, 1.20, 1.40 and 2.00 m/s in a pipe flow circulating seawater device. For each flow velocity, at least three different polarization current densities were chosen to perform galvanostatic cathodic polarization for 7 d. The results showed that the current density demand for an adequate cathodic protection (CP) increased with the flow velocity; the potential could be also polarized to achieve -800 mV vs the silver/silver chlo- ride (seawater) reference electrode (Ag/AgCl (sw)) when the velocity was up to 1.00 m/s; however when the velocity was above 1.20 m/s, erosion-corrosion probably could occur even the polariza- tion potential has achieved the protective potential; the calcareous deposits formed on the steel sur- face were most single magnesium-rich layers. Exceptionally, calcium-rich deposits could form on top of the magnesium-rich layer only when a very high current density was applied.
Published Version
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